Apple II User Manual

ADDITIONAL STRING CONSIDERATIONS

1.  A string may contain from 0 to 255 characters.  All string variable names end in a dollar

    sign ($); for example, A$, B9$, K$, HELLO$.

2.  String matrices may be dimensioned exactly like numeric matrices.  For instance,

    DIM A$(10,10) creates a string matrix of 121 elements, eleven rows by elevon columns

    (rows 0 to 10 and columns 0 to 10).  Each string matrix element is a complete string,

    which can be up to 255 characters in length.

    NAME            EXAMPLE                 PURPOSE/USE

    ----            -------                 -----------

    DIM             25 DIM A$(10,10)        Allocates space for a pointer and length for

                                            each element of a string matrix.  No string

                                            space is allocated.

    LET             27 LET A$="FOO"+V$      Assigns the value of a string expression to

                                            a string variable.  LET is optional.

    =                                       String comparison operators.  Comparison

    >                                       is made on the basis of ASCII codes, a

    <                                       character at a time until a difference is

    <= or =<                                found.  If during the comparison of two

    >= or =>                                strings, the end of one is reached, the

    <>                                      shorter string is considered smaller.

                                            Note that "A " is greater than "A" since

                                            trailing spaces are significant.

    +               30 LET Z$=R$+Q$         String concatenation.  The resulting string

                                            must be less than 256 characters in length

                                            or an LS error will occur.

    INPUT           40 INPUT X$             Reads a string from the keyboard.  String

                                            does not have to be quoted; but if not,

                                            leading blanks will be ignored and the

                                            string will be terminated on a "," or ":"

                                            character.

    READ            50 READ X$              Reads a string from DATA statements

                                            within the program.  Strings do not have

                                            to be quoted; but if they are not, they

                                            are terminated on a "," or ":" character

                                            and leading spaces are ignored.  See

                                            DATA for the format of string data.

    PRINT           60 PRINT X$             Prints the string expression on the

                    70 PRINT "FOO"+A$       display/printer.

300  STATEMENT DEFINITIONS

301  SPECIAL CHARACTERS

    CHARACTER       USE

    ---------       ---

    @               Erases current line being typed, and types a carriage return/line

                    feed.

    DEL             Erases last character typed.  If no more characters are left on

                    the line, types a carriage return/line feed.

    RETURN          A RETURN must end every line typed in.  Returns cursor to

                    the first position (leftmost) on line, and prints the line if the

                    printer is on.

    F1              Interrupts execution of a program or a list command.  F1 has

                    effect when a statement finishes execution, or in the case of

                    interrupting a LIST command, when a complete line has

                    finished printing.  In both cases a return is made to BASIC's